Various forms of nucleic acid are used in a variety of fields. For example, in the field of a recombinant nucleic acid technology, the nucleic acid is required to be used in the form of a probe, a genomic nucleic acid and a plasmid nucleic acid.
Also, in the field of diagnostics, nucleic acid is used in various forms for various purposes. For example, nucleic acid probes are used routinely in the detection and diagnosis of human pathogen. Likewise, nucleic acid is used in the detection of genetic disorders. Nucleic acid is also used in the detection of food pollution substances. Further, nucleic acid is used routinely in locating, identifying and isolating nucleic acid of interest for a variety of reasons ranging from genetic mapping to cloning and recombinant expression.
In many cases, nucleic acid is available in extremely small amounts, and thus isolation and purification procedures are laborious and time consuming. Occasionally, these time consuming and laborious operations are likely to lead to the loss of nucleic acid.
In purifying nucleic acid from samples obtained from serum, urine and bacterial cultures, there is an additional risk of contamination and false-positive result.
One widely known separation and purification methods, there is a method in which nucleic acid is adsorbed to silicon dioxide, silica polymer, magnesium silicate or the like solid phase and then separated and purified by carrying out washing, desorption and the like operations (e.g., JPA-7-51065). This method is excellent in its separation performance, but cannot be said sufficient in terms of convenience, quickness and automation aptitude, and has problems in that the tools and apparatuses to be used in this method are not suited for automation and miniaturization, it is difficult to produce the tools and apparatuses, particularly an adsorption medium, in an industrially large scale with the same performance, and their handling is so inconvenient that they are difficult to be processed in various shapes. Further, due to the fragility of a material and requiring a certain thickness or more to obtain mechanical strength, especially, in order to homogeneously interact DNase on a solid phase when degrading DNA with DNase for selectively recovering RNA from a mixture sample containing DNA and RNA, there are drawbacks such as requiring the DNase solution in a certain amount or more. DNase is relatively expensive, so that this could become a problem in case of selectively recovering RNA which necessity is predicted to increase much more in the future.
Further, one of the methods for separating and purifying nucleic acid simply and effectively is to use a solution for adsorbing nucleic acid onto a solid phase and a solution for desorbing nucleic acid from the solid phase membrane so that there is provided a method for separating and purifying nucleic acid by adsorbing and desorbing onto and from the solid phase comprising an organic polymer having a hydroxyl group on a surface thereof (JPA-2003-128691 and JPA-2004-49108), but more improvement is demanded.
Examples of other related known methods for separating and purifying nucleic acid are using a centrifuge method, magnetic beads and a filter. Further, an apparatus for separating and purifying nucleic acid, which use these methods, have been proposed. For example, an apparatus for separating and purifying nucleic acid using filter, wherein several filter tubes receiving filters are set on a rack, and therein a sample solution containing nucleic acid is injected where the bottom portion of the rack is applied with a sealing agent and sealed with an air chamber to reduce an inner pressure. Simultaneously the sample solution containing nucleic acid is sucked from the discharging side and passed through all filter tube, so as to adsorb nucleic acid onto the filter. Afterwards, a washing solution and a recovering solution are injected and again sucked thereto under reduced pressure so that washing and desorbing are also conducted. An automated apparatus using these procedures has been proposed. (e.g., refer to Japanese Patent No. 2832586).